Method and apparatus for uplink orthogonal frequency division multiple access communication in a WLAN

ABSTRACT

A communication device performs a clear channel assessment (CCA) procedure to determine whether the communication device can transmit in a shared wireless communication medium, wherein the communication device is in a first basic service set (BSS) associated with a virtual access point (AP) implemented by a physical AP, and wherein the first BSS corresponds to a first BSS identifier. Performing the CCA procedure includes: for first signals having the first BSS identifier or having one or more second BSS identifiers corresponding to other virtual APs implemented by the physical AP, comparing energy of the signals to a first threshold; and for first signals determined by the communication device to have one or more third BSS identifiers, wherein the one or more third BSS identifiers correspond to other physical APs, comparing energy of the signals to a second threshold lower than the first threshold.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.14/963,045, filed Dec. 8, 2015, entitled “Methods and Devices forDetermining Channel State,” which claims the benefit of U.S. ProvisionalPatent Application No. 62/089,026, filed Dec. 8, 2014, entitled “BSSColor and Multiple BSSID.” The disclosures of both of the applicationsreferenced above are hereby expressly incorporated herein by referencein their entireties.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to communication networks and,more particularly, to wireless local area networks that utilizeorthogonal frequency division multiplexing (OFDM).

BACKGROUND

The Institute for Electrical and Electronics Engineers (IEEE) 802.11family of Standards (generally “802.11”) has gone through severaliterations over the last decade. In some of the 802.11 standards, suchas 802.11ah and beyond, the identity of the Basic Service Set (BSS)(e.g., as managed by an access point (AP) of the BSS) is indicated in aPhysical Layer Convergence Procedure (PLCP) Protocol Data Unit (PPDU) bya set of bits that described the “color” of the BSS. The color of a BSScorresponds to an identifier (ID) of the BSS that is shorter than a BSSidentifier (BSSID) defined by 802.11. The BSS color may be contained inthe Physical Layer (PHY) Signal (SIG) field in a PHY header of a PPDU,whereas the BSSID is typically included in a media access control (MAC)portion of PPDUs. A device (e.g., an AP or client) in a BSS candetermine whether a PPDU is from the BSS to which the device belongs(the “same-BSS”) or some other BSS (e.g., an overlapping BSS (OBSS)), adevice (e.g., an AP or client) by decoding the SIG field andinterpreting BSS color bits included therein.

One of the newer implementations of 802.11 being discussed is 802.11ax(sometimes referred to as 802.11 HE or 802.11 HEW). 802.11axcontemplates dynamically adjusting the energy level at which a channelis deemed to be clear depending on whether the energy corresponds tosame-BSS signals or to signals from another BSS. Such a scheme helps topromote spatial reuse between neighboring networks.

SUMMARY

In an embodiment, a method includes: determining, at an access point(AP) device, a plurality of respective identifiers of a plurality ofrespective basic service sets (BSSs) corresponding to a plurality ofrespective virtual APs implemented by the AP device; broadcasting, withthe AP device, the plurality of respective identifiers of the pluralityof respective BSSs so that client devices of the plurality of virtualAPs are made aware of all of the identifiers of the plurality ofrespective BSSs; and indicating to one or more client communicationdevices, with the AP device, a single identifier, from among theplurality of respective identifiers, that is to be used in one or moremulti-user transmissions.

In another embodiment, a method includes: determining, at an accesspoint (AP) device, a plurality of identifiers of a plurality ofrespective basic service sets (BSSs) corresponding to a plurality ofrespective virtual APs implemented by the AP device; generating, at theAP device, an orthogonal frequency division multiple access (OFDMA)physical layer (PHY) data unit or a multi-user multiple input multipleoutput (MU-MIMO) PHY data unit that includes data from multiple virtualAPs among the plurality of virtual APs, wherein generating the OFDMA PHYdata unit or the MU MIMO PHY data unit comprises generating a PHYpreamble that includes one or more fields for specifying an identifierof a BSS, wherein the one or more fields are set to a same value; andtransmitting, with the AP device, the OFDMA PHY data unit or the MU MIMOPHY data unit to a group of client devices among the plurality of clientdevices.

In yet another embodiment, a method includes: performing, at thecommunication device, a clear channel assessment (CCA) procedure todetermine whether the communication device can transmit in a sharedwireless communication medium, wherein the communication device is in afirst basic service set (BSS) associated with a virtual access point(AP) implemented by a physical AP, wherein the first BSS corresponds toa first BSS identifier, and wherein performing the CCA procedureincludes: for first signals determined by the communication device tohave the first BSS identifier in PHY preambles of the signals, comparingenergy of the signals to a first threshold, for first signals determinedby the communication device to have one or more second BSS identifiersin PHY preambles of the signals, wherein the one or more second BSSidentifiers correspond to one or more second BSSs of one or more othervirtual APs implemented by the physical AP, comparing energy of thesignals to the first threshold, and for first signals determined by thecommunication device to have one or more third BSS identifiers in PHYpreambles of the signals, wherein the one or more third BSS identifierscorrespond to one or more third BSSs corresponding to one or more otherphysical APs, comparing energy of the signals to a second thresholdlower than the first threshold.

In still another embodiment, a method includes: associating, at acommunication device, with a virtual access point (AP) implemented by aphysical AP, the virtual AP corresponding to a first basic service set(BSS), wherein the first BSS corresponds to a first BSS identifier; aspart of an uplink (UL) orthogonal frequency division multiple access(OFDMA) transmission to the physical AP, generating, at thecommunication device, a signal having i) a physical layer (PHY) preamblewith a field including a second BSS identifier, and ii) a PHY payloadcorresponding to the first BSS; and transmitting, with the communicationdevice, the signal to the physical AP as part of the UL OFDMAtransmission.

In another embodiment, a method for communicating on a wireless networkis carried out on a physical AP, and includes: setting up a plurality ofvirtual access points; assigning a BSS color to each of the plurality ofvirtual access points; and broadcasting a message that identifies eachof the plurality of access points and the BSS color assigned to each ofthe plurality of access points.

In yet another embodiment, a method of determining whether a wirelesscommunication medium is clear is carried out on a client device, andincludes: associating with a first virtual access point (AP) of aplurality of virtual APs implemented by a physical AP; receiving, from aphysical AP, a message identifying the basic service set (BSS) color ofeach of the plurality of virtual APs implemented by the physical AP;detecting a packet data unit; measuring the energy of the packet dataunit; decoding a BSS color from the packet data unit; if the decoded BSScolor is the same as a BSS color in the message from the physical AP,then setting an energy threshold to a first level; if the decoded BSScolor is not the same as any BSS color in the message from the physicalAP, then setting an energy threshold to a second level, wherein thesecond level is higher than the first level; and transmitting orrefraining from transmitting a packet data unit based on a comparison ofthe measured energy and the energy threshold.

In still another embodiment, a method of determining whether a wirelesscommunication medium is clear is carried out on a client device, andincludes: associating with a first virtual access point (AP) of aplurality of virtual APs implemented by a physical AP, wherein the firstvirtual AP has a virtual AP identifier; detecting a packet data unitthat includes a header comprising a basic service set (BSS) color field,wherein the BSS color field comprises a virtual AP identifier part and asegment identifier part; measuring the energy of the packet data unit;decoding the virtual AP part; if the decoded virtual AP part is the sameas the virtual AP identifier of the first virtual AP, then setting anenergy threshold to a first level; if the decoded virtual AP part is notthe same as the virtual AP identifier of the first virtual AP, thensetting an energy threshold to a second level, wherein the second levelis higher than the first level; and transmitting or refraining fromtransmitting a packet data unit based on a comparison of the measuredenergy and the energy threshold.

In various other embodiments, an apparatus comprise one or moreintegrated circuits configured to implement one or more of the methodsdescribed above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example wireless local area network(WLAN), according to an embodiment.

FIG. 2 is diagram of an example multiple basic service set identifier(BSSID) element that is communicated in a wireless network, according toan embodiment.

FIG. 3 is a diagram of two High Efficiency (HE) PPDUs transmitted bydifferent virtual APs, according to an embodiment.

FIG. 4 is a message sequence diagram illustrating transmissions bymultiple client device associated with different virtual APs, accordingto an embodiment.

FIGS. 5A-5C are diagrams of example channel allocation schemes in an 80MHz communication channel, according to various embodiments.

FIGS. 6A, 6B, 6C, and 6D are diagrams illustrating example OFDMsub-channels of an 80 MHz communication channel, according to variousembodiments.

FIG. 7 is a diagram of an example PHY data unit, according to anembodiment.

FIG. 8 is a diagram of an example multi-user PHY data unit, according toan embodiment.

FIG. 9 is a message sequence diagram illustrating transmissions amongmultiple devices, according to an embodiment.

FIG. 10A is a message sequence diagram illustrating multi-usercommunications, according to an embodiment.

FIG. 10B is a diagram of a downlink orthogonal frequency divisionmultiple access (DL OFDMA) transmission of FIG. 10A, according to anembodiment.

FIG. 11A is a message sequence diagram illustrating transmissionsbetween two virtual access points and multiple clients, according to anembodiment.

FIG. 11B is a set of diagrams illustrating transmissions of multipleclients as part of a multi-user transmission illustrated in FIG. 11A,according to an embodiment.

FIG. 12 is a message sequence diagram of transmissions among multipledevices, according to an embodiment.

FIG. 13A is a message sequence diagram illustrating transmissionsbetween two virtual access points and multiple clients, according to anembodiment.

FIG. 13B is a set of diagrams illustrating transmissions of multipleclients as part of a multi-user transmission illustrated in FIG. 13A,according to an embodiment.

FIG. 14 is a flow diagram of an example method for informing devices ina wireless network of network identifiers utilized by multiple basicservice sets (BSSs) implemented in the wireless network, according to anembodiment.

FIG. 15 is a message sequence diagram of transmissions among multipledevices, according to an embodiment.

FIG. 16 is a flow diagram of an example method for determining whether awireless communication medium is busy, according to an embodiment.

FIG. 17 is a flow diagram of an example method for performing amulti-user wireless transmission, according to an embodiment.

FIG. 18 is a flow diagram of an example method for performing atransmission as part of a multi-user wireless transmission, according toan embodiment.

DETAILED DESCRIPTION

In an environment in which a single physical access point (AP)implements a plurality of virtual APs managing a plurality of basicservice sets (BSSs), various techniques described below assist a clientdevice associated with one of the virtual APs to quickly determinewhether a transmission corresponds to one of the BSSs managed by the APor a BSS managed by another physical AP, according to variousembodiments. For example, physical layer (PHY) headers of PHY data unitsmay include respective identifiers of the respective BSSs to which thePHY data units correspond, according to some embodiments. When receivinga PHY data unit, a client device may examine the identifier of the BSSin the PHY header to determine whether the PHY data unit corresponds toa BSS managed by the physical AP with which the client device isassociated, according to some embodiments. Quickly determining whether atransmission corresponds to one of the BSSs managed by the AP or a BSSmanaged by another physical AP may be useful, for example, in some clearchannel assessment (CCA) procedures, according to some embodiments. Forinstance, as merely an illustrative scenario, for a received signal at agiven power level, a client device may determine that a communicationchannel is busy if the client device determines that the signalcorresponds to a transmission in a BSS served by the physical AP towhich the client device is associated; whereas if the client devicedetermines that the signal corresponds to a transmission in a BSS servedby a different physical AP, the client device may determine that acommunication channel is clear, according to an illustrative embodiment.

In some embodiments, to facilitate multi-user transmissions having datafrom multiple BSSs served by a single physical AP, a PHY preamble mayinclude only one BSS identifier.

FIG. 1 is a block diagram of an example wireless local area network(WLAN) 10, according to an embodiment. An AP 14 includes a hostprocessor 15 coupled to a network interface device 16. The networkinterface device 16 includes a medium access control (MAC) processingunit 18 and PHY processing unit 20. The PHY processing unit 20 includesa plurality of transceivers 21, and the transceivers 21 are coupled to aplurality of antennas 24. Although three transceivers 21 and threeantennas 24 are illustrated in FIG. 1, the AP 14 includes differentnumbers (e.g., 1, 2, 4, 5, etc.) of transceivers 21 and antennas 24 inother embodiments.

In various embodiments, the network interface device 16 is implementedon one or more integrated circuit (IC) devices. For example, in anembodiment, at least a portion of the MAC processing unit 18 isimplemented on a first IC device and at least a portion of the PHYprocessing unit 20 is implemented on a second IC device. As anotherexample, at least a portion of the MAC processing unit 18 and at least aportion of the PHY processing unit 20 are implemented on a single ICdevice.

The WLAN 10 includes a plurality of client stations 25. Although fourclient stations 25 are illustrated in FIG. 1, the WLAN 10 includesdifferent numbers (e.g., 1, 2, 3, 5, 6, etc.) of client stations 25 invarious scenarios and embodiments.

A client station 25-1 includes a host processor 26 coupled to a networkinterface device 27. The network interface device 27 includes a MACprocessing unit 28 and a PHY processing unit 29. The PHY processing unit29 includes a plurality of transceivers 30, and the transceivers 30 arecoupled to a plurality of antennas 34. Although three transceivers 30and three antennas 34 are illustrated in FIG. 1, the client station 25-1includes different numbers (e.g., 1, 2, 4, 5, etc.) of transceivers 30and antennas 34 in other embodiments.

In various embodiments, the network interface device 27 is implementedon one or more IC devices. For example, in an embodiment, at least aportion of the MAC processing unit 28 is implemented on a first ICdevice and at least a portion of the PHY processing unit 29 isimplemented on a second IC device. As another example, at least aportion of the MAC processing unit 28 and at least a portion of the PHYprocessing unit 29 are implemented on a single IC device.

In an embodiment, one or more of the client stations 25-2, 25-3, and25-4 has a structure the same as or similar to the client station 25-1.In these embodiments, the client stations 25 structured like the clientstation 25-1 have the same or a different number of transceivers andantennas. For example, the client station 25-2 has only two transceiversand two antennas (not shown), according to an embodiment.

In an embodiment, the AP is configured to operate according to awireless communication protocol that utilizes Orthogonal FrequencyMultiple Division Access (OFDMA) technology and/or multi-user multipleinput, multiple output (MU-MIMO) technology. The wireless communicationprotocol is sometimes referred to herein as the IEEE 802.11ax Standard,the high efficiency WiFi protocol, the HEW protocol, the HE protocol, or802.11 HE.

In an embodiment, the AP 14 (e.g., the network interface device 16 ofthe AP 14) is configured to transmit independent data simultaneously tomultiple client stations 25 via different spatial streams (e.g.,downlink (DL) MU-MIMO) and/or via different OFDM sub-channels (e.g., DLOFDMA). In an embodiment, the AP 14 (e.g., the network interface device16 of the AP 14) is configured to receive independent datasimultaneously from multiple client stations 25 via different spatialstreams (e.g., uplink (UL) MU-MIMO) and/or via different OFDMsub-channels (e.g., UL OFDMA). In some embodiments, two or more of theclient stations 25 are configured to receive respective data streamsthat are transmitted simultaneously by the AP 14 (e.g., DL OFDMA and/orDL MU-MIMO). For example, in one embodiment, the network interfacedevice 27 is configured to receive a data stream among a plurality ofindependent data streams transmitted simultaneously by the AP 14 tomultiple client stations 25 via different spatial streams and/or viadifferent OFDM sub-channels. In other embodiments, two or more of theclient stations 25 additionally or alternatively are configured totransmit corresponding data streams to the AP 14 such that the AP 14receives the data streams simultaneously (e.g., UL OFDMA and/or ULMU-MIMO). For example, in one embodiment, the network interface device27 is configured to transmit a data stream while one or more otherclient devices 25 transmit one or more other independent data streamssimultaneously to the AP 14 via different spatial streams and/or viadifferent OFDM sub-channels.

In an embodiment, the AP 14 and the client stations 25 contend forcommunication medium using carrier sense multiple access with collisionavoidance (CSMA/CA) protocol or another suitable medium access protocol.In an embodiment, the AP 14 and the client stations employ a clearchannel assessment (CCA) procedure, in which the AP/client stationdetermines the energy level of the medium in order to determine whetherthe medium is busy or idle. If the medium is idle, the device cantransmit. If the medium is busy, the device waits a backoff period andthen checks the medium again after the backoff period. A thresholdenergy level for determining whether the medium is idle or busy maydepend upon the bandwidth of the channel being used by the device and onwhether the energy corresponds to a transmission that conforms to thewireless communication protocol. For example, in 802.11, if the channelbandwidth is 20 Megahertz (MHz), the threshold level is −82decibel-milliwatts (dBm) for energy from valid 802.11 transmissions. Forchannel bandwidths of 40 MHz, 80 MHz, and 160 MHz, the threshold levelsare −79 dBm, −76 dBm, and −73 dBm, respectively. For energy notidentified by the device as a valid 802.11 signal, the threshold levelis −62 dBm.

In an embodiment, the AP 14 and the client stations 25 employ a dynamicCCA procedure. In the dynamic CCA procedure, the AP/client device mayuse a higher threshold level for valid 802.11 signals from a differentBSS as compared to the threshold level for valid 802.11 signals from thesame BSS. For example, an AP/client device might deem a 20 MHz channelto be idle if the energy level of an 802.11 signal from another BSS isless than −62 dBm (i.e., the same threshold level as for energycorresponding to signals that are not valid 802.11 signals), but deemthe channel to be busy if the energy level of an 802.11 signal from thesame BSS is greater than −82 dBm. Thus, an energy level of −70 dBm of avalid 802.11 signal from a different BSS would result in the devicedetermining that the channel is idle, while an energy level of −70 dBmresulting from same-BSS signals would result in the device determiningthat the channel is busy. Allowing a higher CCA level for transmissionscorresponding to another BSS helps to promote spatial reuse betweendifferent BSSs, at least in some embodiments and/or scenarios. In someembodiments, the AP 14 and/or the client stations 25 are able toeffectively override dynamic CCA when they determine that an energylevel is based on transmissions to or from the same physical AP(although different virtual APs).

Further, in an embodiment, the AP 14 or a client station 25 dynamicallyselects a bandwidth for a transmission based on channels available forthe transmission. In some embodiments, communication between the AP 14and the client stations 25 can occur in a primary channel of the WLAN10, in both a primary and a secondary channel of the WLAN 10,exclusively on a secondary channel of the WLAN 10, etc.

In an embodiment, the AP 14 is configured to transmit differentindependent data to different client stations 25 simultaneously bygenerating an OFDMA data unit that includes different independent datamodulated in respective sub-channels of a communication channel. In anembodiment, each sub-channel incudes one or more sub-channel blocks,each sub-channel block corresponding to a set of sub-carriers within theOFDMA data unit. In an embodiment, the AP 14 allocates differentsub-channels to different client stations and generates the OFDMA dataunit that respective data is modulated in sub-channel blockscorresponding to the sub-channels allocated to the client stations. TheAP may assign the primary and the non-primary communication channels inany suitable manner to the one or more client stations, in variousembodiments.

In an embodiment, the AP 14 (e.g., the host processor 15 and/or thenetwork interface device 16 (e.g., the MAC processor device 18)) sets upa plurality of virtual APs, represented in FIG. 1 by a first virtual AP35-1 and a second virtual AP 35-2. Each virtual AP uses the resources ofthe AP 14 to provide a BSS to the WLAN 10, effectively appearing to theclients 25 as multiple WLANs. To distinguish between the AP 14 and thevirtual APs 35-1 and 35-2, the AP 14 will sometimes be referred toherein as a “physical AP.” Each virtual AP 35 corresponds to arespective Basic Service Set Identification (BSSID). In an embodiment,the physical AP 14 (e.g., one of the virtual APs) broadcasts a beaconthat advertises the BSSIDs of the virtual APs 35. In an embodiment, theBSSIDs are contained in a multiple BSSID information element of thebeacon. FIG. 2 is a diagram of an example multiple BSSID informationelement 200, according to an embodiment. The BSSIDs are included in thefield 220, in an embodiment.

Referring again to FIG. 1, the virtual APs 35 may utilize a singlebeacon and may broadcast, via the single beacon, one or more properties,parameter values, etc., shared by the virtual APs, according to variousembodiments. For example, in an embodiment, the following informationelements in a beacon are common for all of the virtual APs 35 (e.g.,each information element provides information that is same for thevirtual APs): a Timestamp, a Beacon Interval, a Direct Sequence SpreadSpectrum (DSSS) Parameter Set, a Frequency Hopping (FH) Parameter Set,an Independent BSS (IBSS) Parameter Set, a Country, FH Parameters, a FHPattern Table, a Channel Switch Assignment, an Extended Channel SwitchAnnouncement, Supported Operating Classes, an IBSS Dynamic FrequencySelection (DFS), Extended Rate Physical (ERP) Information, HighThroughput (HT) Capabilities, HT Operation elements, etc. Because theseelements are common amongst the virtual APs, in an embodiment, thephysical AP 14 does not include these elements in the NontransmittedBSSID Profile field 220 (FIG. 2). In an embodiment, the values of theseelements for each nontransmitted BSSID are always the same as thecorresponding transmitted BSSID element values. In an embodiment, thefirst 2^(n) bits of the Traffic Indication Map (TIM) are reserved forbroadcast/multicast for each BSS, where n is a suitable positiveinteger. In an embodiment, the value of n is reported in the multipleBSSID element. In an embodiment, the remainder of the Association ID(AID) space is shared by all BSSs. Furthermore, in an embodiment, eachBSS (e.g., each virtual AP) has a respective Delivery Traffic IndicationMessage (DTIM) interval that need not be the same as the other BSSs.

In some embodiments, multiple A-MPDUs to/from multiple STAs are includedin a single MU transmission. In some embodiments, an A-MPDU in a singleMU transmission includes MPDUs to/from multiple STAs. In someembodiments, at most one A-MPDU can be included in a single SUtransmission.

FIG. 3 is a diagram of an example orthogonal frequency divisionmultiplexing (OFDM) multi-user (MU) transmission corresponding to twoPPDUs (e.g., 802.11 HE PPDUs) simultaneously transmitted by a physicalAP, where each PPDU corresponds to a different virtual AP having a sameBSS color value, according to an embodiment. In the scenario illustratedin FIG. 3, a first PPDU 304 is transmitted to a first client device(STA1) via a 20 MHz primary channel of a first BSS served by a firstvirtual AP; and a second PPDU 308 is transmitted to a second clientdevice (STA2) via a 20 MHz secondary channel of a second BSS served by asecond virtual AP. In an embodiment, the first BSS and the second BSShave the same 20 MHz primary channel.

The first PPDU 304 includes a first PHY preamble 320 having a first HEsignal (SIG) field (HE SIG), and the second PPDU 308 includes a secondPHY preamble 324 having a second SIG field (HE SIG). In the scenarioillustrated in FIG. 3, the first virtual AP has been assigned a firstidentifier (referred to herein as a “color”), and the second virtual APhas been assigned the same first identifier (or color). In someembodiments, the color is not globally unique. In some embodiments, arange of possible colors is smaller than a range of possible BSSIDs, andthus each color can be represented by less bits than a BSSID. In anembodiment, each HE SIG field includes a color field to indicate thecolor of the BSS to which the PPDU corresponds. Thus, in an embodiment,the color field in the first HE SIG field in the preamble 320 has avalue corresponding to the first identifier (color), and the color fieldin the second HE SIG field in the preamble 324 has a value correspondingto the same first identifier (color).

When different virtual APs have different BSS colors, A-MPDUstransmitted to STAs which are associated with different virtual APscannot be in one DL MU transmission, and A-MPDUs transmitted from STAswhich are associated with different virtual APs cannot be in one UL MUtransmission. For instance, in some embodiments, HE SIG fields of MUtransmissions use a whole MU transmission bandwidth, e.g. in a 40 MHz MUtransmission, HE SIGs from different virtual APs occupy the same 40 MHzbandwidth.

On the other hand, an HE SIG of a SU PPDU includes the BSS color of thevirtual AP that is the transmitter or the receiver of the SU PPDU. Whendifferent virtual APs have different BSS colors, the HE SIGs of SU PPDUstransmitted by different virtual APs have different BSS colors, and theBSS color of SU PPDUs transmitted to different virtual APs havedifferent BSS colors. When the second virtual AP transmits a SU HE PPDUto an associated STA, the HE SIG of the SU HE PPDU includes the BSScolor of the second virtual AP. Consequently, devices associated withthe first virtual AP may utilize a CCA energy threshold corresponding toan “other BSS” with transmissions from the second virtual AP, and viceversa, even though the transmissions are from the same physical AP.

FIG. 4 is a message sequence diagram of multiple transmissions amongSTA1, STA2, a first virtual AP (AP1) and a second virtual AP (AP2). Inthis example, STA1 is associated with AP1, whose BSS color will bereferred to as Color 1, and STA2 is associated with AP2, whose BSS colorwill be referred to as Color 2, which is different than Color 1. At timet1, STA1 begins transmitting an HE PPDU 404 to AP1. STA2 has its own HEPPDU that STA2 needs to transmit to AP2. STA2 therefore carries out aCCA procedure to determine whether the channel is clear. In carrying outthe CCA procedure, STA2 detects and decodes the HE SIG of HE PPDU 404,identifies the BSS color associated with HE PPDU 404 as Color 1, and,because Color 1 is different than the color of AP2 with which STA2 isassociated, STA2 uses the dynamic CCA level (i.e., allows for a higherlevel of 802.11-based energy than a standard CCA level associated with802.11 transmissions in a same BSS). Using the dynamic CCA level, STA2concludes that the channel is clear and, at time t2, begins transmittingan HE PPDU 408 to AP2. However, because AP1 and AP2 exist areimplemented by a same physical AP, a collision occurs.

FIGS. 5A-5C are diagrams of example channel allocation schemes in an 80MHz communication channel, according to various embodiments. In each ofFIGS. 5A-5C, respective 20 MHz sub-channels are allocated to each offour client stations 25 (STA1, STA2, STA3 and STA4). In FIG. 5A, each ofthe sub-channels, allocated to a particular one of STA1, STA2, STA3 andSTA4, includes of a single sub-channel block of adjacent sub-carriersallocated to the particular station. In FIG. 5B, each of thesub-channels, allocated to a particular one of STA1, STA2, STA3 andSTA4, includes four respective sub-channel blocks uniformly spaced overthe entire 80 MHz channel. In FIG. 5C, each of the sub-channels includesof four respective non-uniformly (e.g., randomly) spaced over the entire80 MHz channel. In each of FIGS. 5B and 5C, each of the sub-channelblocks allocated to a particular client station includes a block ofadjacent sub-carriers, wherein the block of adjacent sub-carriersincludes a subset of sub-carriers, of the 80 MHz channel, allocated tothe particular client station, according to an embodiment.

In some embodiments, a sub-channel having a suitable bandwidth less thanthe smallest bandwidth of the WLAN can be allocated to a client station.For example, in some embodiments in which the smallest channel bandwidthof the WLAN 10 is 20 MHz, sub-channel having bandwidth less than 20 MHz,such as sub-channels having bandwidths of 10 MHz and/or 5 MHz can beallocated to client stations, in at least some scenarios.

FIGS. 6A, 6B, 6C, and 6D are diagrams illustrating example OFDMsub-channels of an 80 MHz communication channel, according to variousembodiments. In FIG. 6A, the communication channel is partitioned intofour contiguous sub-channels, each having a bandwidth of 20 MHz. TheOFDM sub-channels include independent data streams for four clientstations. In FIG. 6B, the communication channel is partitioned into twocontiguous sub-channel channels, each having a bandwidth of 40 MHz. TheOFDM sub-channels include independent data streams for two clientstations. In FIG. 6C, the communication channel is partitioned intothree contiguous OFDM sub-channels. Two OFDM sub-channels each have abandwidth of 20 MHz. The remaining OFDM sub-channel has a bandwidth of40 MHz. The OFDM sub-channels include independent data streams for threeclient stations. In FIG. 6D, the communication channel is partitionedinto four contiguous OFDM sub-channels. Two OFDM sub-channels each havea bandwidth of 10 MHz, one OFDM sub-channel has a bandwidth of 20 MHz,and one OFDM sub-channel has a bandwidth of 40 MHz. The OFDMsub-channels include independent data streams for three client stations.

Although in FIGS. 6A, 6B, 6C, and 6D the OFDM sub-channels arecontiguous across the communication channel, in other embodiments theOFDM sub-channels are not contiguous across the communication channel(i.e., there are one or more gaps between the OFDM sub-channels). In anembodiment, each gap is at least as wide as one of the OFDM sub-channelblocks. In another embodiment, at least one gap is less than thebandwidth of an OFDM sub-channel block. In another embodiment, at leastone gap is at least as wide as 1 MHz. In one embodiment, the AP includesa plurality of radios and different OFDM sub-channel blocks aretransmitted using different radios.

In FIGS. 6A, 6B, 6C, and 6D, each sub-channel corresponds to a singlesub-channel block of adjacent sub-carriers allocated to a particularclient station. In other embodiments, each of at least some sub-channelsof an 80 MHz channel corresponds to several sub-channel blocks, eachhaving adjacent sub-carriers, where the several sub-channel blockscollectively comprise the sub-carriers allocated to a particular clientstation. The several sub-channel blocks corresponding to a particularclient station are uniformly or non-uniformly distributed over the 80MHz channel, for example as described above with respect to FIGS. 6B and6C, in some embodiments. In such embodiments, an independent data streamfor the particular client station is accordingly distributed over the 80MHz channel.

FIG. 7 is a diagram of an OFDM data unit 700, according to anembodiment. In some embodiments, an AP (e.g., the AP 14) is configuredto generate and transmit OFDM data units having a format such asillustrated in FIG. 7 to client devices (e.g., client devices 25),and/or a client station (e.g., the client station 25-1) is configured totransmit the data unit 700 to the AP (e.g., the AP 14). The data unit700 conforms to the HEW protocol and occupies an 80 MHz band. In otherembodiments, data units similar to the data unit 700 occupy differentsuitable bandwidths such as 20 MHz, 40 MHz, 120 MHz, 160 MHz, or anysuitable bandwidth. The data unit 700 is suitable for “mixed mode”situations, such as when a WLAN 10 includes a client station thatconforms to a legacy protocol, but not the HEW protocol. The data unit700 can be utilized in other situations as well.

The data unit 700 includes a PHY preamble having four legacy shorttraining fields (L-STFs) 705; four legacy long training fields (L-LTFs)710; four legacy signal fields (L-SIGs) 715; four first high efficiencyWLAN signal fields (HEW-SIGAs) 720; four second high efficiency WLANsignal fields (HEW-SIGBs) 722; a high efficiency WLAN short trainingfield (HEW-STF) 725; and N high efficiency WLAN long training fields(HEW-LTFs) 730, where N is an integer. The data unit 700 also includes ahigh efficiency WLAN data portion (HEW-DATA) 740. The L-STFs 705, theL-LTFs 710, and the L-SIGs 715 form a legacy portion of the PHYpreamble. The HEW-SIGA 720, the HEW HEW-SIGBs 722; the HEW-STF 725, andthe HEW-LTFs 730 form a high efficiency WLAN (HEW) portion of the PHYpreamble. In an embodiment, a color field is included in the HEW-SIGAs720. In another embodiment, the color field is included in the HEW-SIGBs 722. In an embodiment, each STA transmits its PHY SIG only in 20 MHzchannels that overlap with the subchannel in which the STA istransmitting. In another embodiment, each STA transmit its PHY SIG inall 20 MHz channels of the MU transmission, and, in an embodiment, thecontent of the PHY SIGs by multiple STAs in each 20 MHz channel is thesame. In an embodiment, the PHY SIGs by multiple STAs are made to havethe same content so that other stations can properly decode the contentof the PHY SIG. For instance, if the content of different PHY SIGs wasdifferent (e.g., different color values), this may garble the content ofthe PHY SIGs when received by other communication devices, at least insome embodiments and/or scenarios.

Each of the L-STFs 705, each of the L-LTFs 710, each of the L-SIGs 715,each of the HEW-SIGAs 720, and each of the HEW-SIGBs 722 occupy a 20 MHzband, in one embodiment. The data unit 700 is described as having an 80MHz contiguous bandwidth for the purposes of illustrating an exampleframe format, but such frame format is applicable to other suitablebandwidths (including noncontiguous bandwidths). For instance, althoughthe preamble of the data unit 700 includes four of each of the L-STFs705, the L-LTFs 710, the L-SIGs 715, the HEW-SIGAs 720, and theHEW-SIGBs 722 in other embodiments in which an OFDM data unit occupies acumulative bandwidth other than 80 MHz, such as 20 MHz, 40 MHz, 120 MHz,160 MHz, etc., a different suitable number of the L-STFs 705, the L-LTFs710, the L-SIGs 715, the HEW-SIGAs 720, and the HEW-SIGBs 722 areutilized accordingly. For example, for an OFDM data unit occupying a 20MHz cumulative bandwidth, the data unit includes one of each of theL-STFs 705, the L-LTFs 710, the L-SIGs 715, the HEW-SIGAs 720, and theHEW-SIGBs 722; a 40 MHz bandwidth OFDM data unit includes two of each ofthe fields 705, 710, 715, 720, and 722; a 120 MHz bandwidth OFDM dataunit includes six of each of the fields 705, 710, 715, 720, and 722; a160 MHz bandwidth OFDM data unit includes eight of each of the fields705, 710, 715, 720, and 722, and so on, according to some embodiments.

In the example data unit 700, each of the HEW-STF 725, the HEW-LTFs 730,and the HEW-DATA 740 occupy the entire 80 MHz cumulative bandwidth ofthe data unit 700. Similarly, in the case of an OFDM data unitconforming to the HEW protocol and occupying a cumulative bandwidth suchas 20 MHz, 40 MHz, 120 MHz, or 160 MHz, each of the HEW-STF 725, theHEW-LTFs 730, and the HEW-DATA 740 occupy the corresponding entirecumulative bandwidth of the data unit, in some embodiments.

In some embodiments, the 80 MHz band of the data unit 700 is notcontiguous, but includes two or more smaller bands, such as two 40 MHzbands, separated in frequency. Similarly, for other OFDM data unitshaving different cumulative bandwidths, such as a 160 MHz cumulativebandwidth, in some embodiments the band is not contiguous in frequency.Thus, for example, the L-STFs 705, the L-LTFs 710, the L-SIGs 715, theHEW-SIGAs 720, and the HEW-SIGBs 722 occupy two or more bands that areseparated from each other in frequency, and adjacent bands are separatedin frequency by at least one MHz, at least five MHz, at least 10 MHz, atleast 20 MHz, for example, in some embodiments.

According to an embodiment, each of the L-STFs 705 and each of theL-LTFs 710 have a format as specified in a legacy protocol such as theIEEE 802.11a Standard, the IEEE 802.11n Standard, and/or the IEEE802.11ac Standard. In an embodiment, each of the L-SIGs 715 has a formatat least substantially as specified in legacy protocol (e.g., the IEEE802.11a Standard, the IEEE 802.11n Standard, and/or the IEEE 802.11acStandard). In such embodiments, the length and rate subfields in theL-SIGs 715 is set to indicate a duration T corresponding to theremainder of the data unit 700 after the legacy portion. This permitsclient stations that are not configured according to the HEW protocol todetermine an end of the data unit 700 for carrier sense multipleaccess/collision avoidance (CSMA/CA) purposes, for example. For example,legacy client stations determine the duration of the remainder of thedata unit 700 and refrain from accessing the medium (or at leasttransmitting in the medium) for the duration of the remainder of thedata unit 700, in an embodiment. In other embodiments, each of theL-SIGs 715 has a format at least substantially as specified in legacyprotocol (e.g., the IEEE 802.11a Standard, the IEEE 802.11n Standard,and/or the IEEE 802.11ac Standard) but with length field in the L-SIGs715 set to indicate a duration of the time remaining in a transmissionopportunity during which the data unit 700 is transmitted. In suchembodiments, client stations that are not configured according to theHEW protocol determine an end of the TXOP and refrain from accessing themedium (or at least transmitting in the medium) for the duration of theTXOP, in an embodiment.

In the data unit 700, frequency domain symbols of the legacy portion arerepeated over four 20 MHz subbands of the 80 MHz band. Legacy clientstations that are configured to operate with 20 MHz bandwidth willrecognize a legacy preamble in any of the 20 MHz subbands. In someembodiments, the modulations of the different 20 MHz subband signals arerotated by different suitable angles. In one example, a first subband isrotated 0 degrees, a second subband is rotated 90 degrees, a thirdsubband is rotated 180 degrees, and a fourth subband is rotated 270degrees, in an embodiment. In other examples, different suitablerotations are utilized. As just one example, a first subband is rotated45 degrees, a second subband is rotated 90 degrees, a third subband isrotated −45 degrees, and a fourth subband is rotated −90 degrees, in anembodiment.

In some embodiments, the modulations of the HEW-SIGAs 720 in thedifferent 20 MHz subbands is rotated by different angles. In oneexample, a first subband is rotated 0 degrees, a second subband isrotated 90 degrees, a third subband is rotated 180 degrees, and a fourthsubband is rotated 270 degrees, in an embodiment. In other examples,different suitable rotations are utilized. As just one example, a firstsubband is rotated 45 degrees, a second subband is rotated 90 degrees, athird subband is rotated −45 degrees, and a fourth subband is rotated−90 degrees, in an embodiment. In an embodiment, the same rotationsutilized in the legacy portion are utilized for the HEW-SIGAs 720. Insome embodiments, the modulations of the HEW-SIGB s 722 in the different20 MHz subbands are similarly rotated by different angles. In at leastsome examples, the HEW-SIGAs 720 are collectively referred to as asingle high efficiency WLAN signal field (HEW-SIGA) 720. In at leastsome examples, the HEW-SIGBs 722 are collectively referred to as asingle high efficiency WLAN signal field (HEW-SIGB) 722.

In an embodiment, the data unit 700 is a single user data unit thatincludes data for only a single AP or only a single client device 25. Inanother embodiment, the data unit 700 is a multi-user data unit thatincludes independent data streams for multiple client stations 25 overrespective spatial streams. In an embodiment in which the data unit 700is a multi-user data unit, a portion of the data unit 700 (e.g., theL-STFs 705, the L-LTFs 710, the L-SIGs 715, the HEW-SIGAs 720, and theHEW-SIGBs 722) is unsteered or omnidirectional (or “omnidirectional” or“pseudo-omnidirectional”; the terms “unsteered” and “omnidirectional” asused herein are intended to also encompass the term“pseudo-omnidirectional”) and includes data that is common to allintended recipients of the data unit 700. The data unit 700 furtherincludes a second portion (e.g., the HEW-STF 725, the HEW-LTFs 730, andthe HEW-DATA portion 740) in which beamforming is applied to differentspatial streams to shape, or beamform, transmission over thecorresponding spatial streams to particular client stations 25. In somesuch embodiments, the steered portion of the data unit 700 includesdifferent (e.g., “user-specific”) content transmitted over differentspatial streams to different ones of the client stations 25.

In some embodiments, the AP 14 is configured to transmit respective OFDMdata units, such as the OFDM data unit 700, simultaneously to multipleclient stations 25 as parts of a downlink OFDMA transmission from the AP14 to the multiple client stations 25. In an embodiment, the AP 14transmits the respective OFDM data units in respective sub-channelsallocated to the client stations. Similarly, in an embodiment, multipleclient stations 25 transmit respective OFDM data units, such as the OFDMdata unit 700, simultaneously to the AP 14 as parts of an uplink OFDMAtransmission from the multiple client stations 25 to the AP 14. In anembodiment, the client stations 25 transmit the respective OFDM dataunits in respective sub-channels allocated to the client stations 25. Inan embodiment, a sub-channel allocated to a particular client stationcorresponds to a single sub-channel block of adjacent sub-carriers ofthe communication channel (e.g., as illustrated in FIG. 5A). In anembodiment, a sub-channel allocated to a particular client stationincludes several sub-channel blocks of adjacent sub-carriers, eachsub-channel block having a set of sub-carriers allocated to theparticular client station. In an embodiment, the several sub-channelblocks corresponding to a particular client station are uniformlydistributed over the communication channel (e.g., as illustrated in FIG.5B). In another embodiment, the several sub-channel blocks are notnecessarily uniformly distributed over the communication channel. Forexample, the several sub-channel blocks are randomly distributed overthe communication channel (e.g., as illustrated in FIG. 5C), or aredistributed according to another suitable distribution scheme over thecommunication channel, in some embodiments.

In some embodiments, the uplink data units (e.g., transmitted from aclient device to an AP) omit HEW-SIGBs. For instance, in someembodiments, the AP instructs client devices regarding which parameters(e.g., MCS, number of spatial streams, etc.) to use when transmitting tothe AP, and thus such parameters need not be included in the PHYpreamble of uplink data units. Thus, this allows omission of theHEW-SIGBs from uplink data units.

In some embodiments, single user (SU) data units omit HEW-SIGBs. Forinstance, in some embodiments, some parameters in the HEW-SIGB relate tomulti-user transmissions, and other parameters (e.g., MCS, number ofspatial streams, etc.) in the HEW-SIGB can be included in the HEW-SIGA.Thus, this allows omission of the HEW-SIGBs from SU data units.

In some embodiments, the HEW-SIGB(s) are positioned after the HEW-LTFs730. In such embodiments, the HEW-SIGB(s) occupy the entire cumulativebandwidth of the data unit 700. For example, in the case of an OFDM dataunit conforming to the HEW protocol and occupying a cumulative bandwidthsuch as 20 MHz, 40 MHz, 120 MHz, or 160 MHz, the HEW-SIGB(s) thecorresponding entire cumulative bandwidth of the data unit, in someembodiments. In such embodiments, beamforming is applied to differentspatial streams to shape, or beamform, HEW-SIGBs over the correspondingspatial streams to particular client stations 25.

In some embodiments, further signal (SIG) fields are included in the PHYpreamble and positioned after the HEW-LTFs 730. In such embodiments,beamforming is applied to different spatial streams to shape, orbeamform, the further SIG fields over the corresponding spatial streamsto particular client stations 25.

FIG. 8 is a diagram of an example OFDMA data unit 800, according to anembodiment. The OFDMA data unit 800 includes a plurality of OFDM dataunits 802. Respective ones of the data units 802 include independentdata streams transmitted to, or received from, respective ones of twoclient devices 25. In an embodiment, each OFDM data unit 802 is the sameas or similar to the OFDM data unit 700 of FIG. 7. In an embodiment, theAP 14 transmits the OFDM data units 802 to different client stations 25via respective OFDM sub-channels within a composite channel spanned bythe OFDMA data unit 800. In another embodiment, different clientstations 25 transmit respective OFDM data units 802 to the AP 14 inrespective OFDM sub-channels within the composite channel spanned by theOFDMA data unit 800. In such an embodiment, the AP 14 receives the OFDMdata units 802 from the client stations 25 via respective OFDMsub-channels of within the composite channel spanned by the OFDMA dataunit 800. Although the data unit 800 is illustrated in FIG. 8 asincluding only two data units 802 transmitted to, or received from, onlytwo client stations 25, the data unit 800 includes more than two (e.g.,3, 4, 5, 6, etc.) data units 802 transmitted to, or received from, morethan two (e.g., 3, 4, 5, 6, etc.) client stations 25, in otherembodiments.

Each of the OFDM data units 802 conforms to a communication protocolthat defines OFDMA communication, such as the HEW communicationprotocol, in an embodiment. In an embodiment in which the OFDMA dataunit 800 corresponds to a downlink (DL) OFDMA data unit, the OFDMA dataunit 800 is generated by the AP 14 such that each OFDM data unit 802 istransmitted to a respective client station 25 via a respectivesub-channel allocated for downlink transmission of the OFDMA data unit800 to the client station. Similarly, an embodiment in which the OFDMAdata unit 800 corresponds to an uplink (UL) OFDMA data unit, the AP 14receives the OFDM data units 802 via respective sub-channels allocatedfor uplink transmission of the OFDM data units 802 from the clientstations, in an embodiment. For example, the OFDM data unit 802-1 istransmitted via a first 40 MHz sub-channel, and the OFDM data unit 802-2is transmitted via a second 40 MHz sub-channel, in an embodiment.

In an embodiment, each of the OFDM data units 802 includes a preambleincluding one or more L-STFs 804, one or more L-LTFs 806, one or moreL-SIGs 808, one or more HEW-SIG-As 810, N HEW-LTFs, and a HEW-SIGB 814.Additionally, each OFDM data unit 802 includes a HEW-DATA portion 818.In an embodiment, each L-STF field 804, each L-LTF field 806, each L-SIGfield 808, each HEW-SIGA field 810, and each HEW-SIGB field 811 occupiesa smallest channel bandwidth supported by the WLAN 10 (e.g., 20 MHz). Inan embodiment, if an OFDM data unit 802 occupies a bandwidth that isgreater than the smallest channel bandwidth of the WLAN 10, then eachL-STF field 804, each L-LTF field 806, each L-SIG field 808, eachHEW-SIGA field 810, and each HEW-SIGB field 811 is duplicated in eachsmallest channel bandwidth portion of the OFDM data unit 802 (e.g., ineach 20 MHz portion of the data unit 802). On the other hand, eachHEW-STF field 812, each HEW-LTF field 814, and each HEW data portion 818occupies an entire bandwidth of the corresponding OFDM data unit 802, inan embodiment.

In an embodiment, padding is used in one or more of the OFDM data units802 to equalize lengths of the OFDM data units 802. Accordingly, thelength of each of the OFDM data units 802 correspond to the length ofthe OFDMA data unit 802, in this embodiment. Ensuring that the OFDM dataunits 802 are of equal lengths facilitates synchronizing transmission ofacknowledgment frames by client stations 25 that receive the data units802, in an embodiment. In an embodiment, each of one or more of the OFDMdata units 802 includes an aggregate MAC protocol data unit (A-MPDU)that includes multiple aggregated MAC protocol data units (MPDUs), whichis in turn included in a PHY protocol data unit (PPDU). In anotherembodiment, each of one or more of the OFDM data units 802 includes asingle MPDU, which is in turn included in a PPDU. In an embodiment,padding (e.g., zero-padding) within one or more of the A-MPDUs 802 orsingle MPDUs 802 is used to equalize the lengths of the data units 802.

In an embodiment, the AP 14 forms groups of client stations 25 forsimultaneous downlink transmissions to client stations 25 and/orsimultaneous uplink transmissions by client stations 25. To this end,the AP 14 allocates respective sub-channels to client stations 25 withina group of client stations 25 and/or allocates respective spatialstreams to client stations 25, in embodiments. In an embodiment and/orscenario, the AP 14 then transmits one or more OFDMA data units to theclient stations 25 in a group using the respective sub-channelsallocated to the client stations 25 within the group and/or transmitsone or more MU MIMO data units to client stations 25 in a group usingrespective spatial streams allocated to the client stations 25 withinthe group. Each group of client stations 25 includes two or more clientstations 25, in an embodiment. In an embodiment, the AP 14 dynamicallygroups client stations to one MU transmission without group management.In an embodiment, the AP 14 notifies the groups that a station belongsto a group through a management frame exchange. A particular clientstation 25 belongs to one or more groups of the client stations 25, inan embodiment. Thus, for example, a first group of client stations 25includes the client station 25-1 and the client station 25-2, and asecond group of client stations 25 includes the client station 25-1 andthe client stations 25-3, in an example embodiment and/or scenario.Accordingly, the client station 25-1 belongs to the first group ofclient stations 25 and to the second group of client stations 25, inthis example embodiment and/or scenario.

In an embodiment, a color field is included in the HEW-SIGAs 810. Inanother embodiment, the color field is included in the HEW-SIGBs 811.

In some embodiments, the uplink (UL) OFDMA data units (e.g., transmittedfrom a client device to an AP) omit HEW-SIGBs. For instance, in someembodiments, the AP instructs client devices regarding which parameters(e.g., MCS, number of spatial streams, etc.) to use when transmitting tothe AP, and thus such parameters need not be included in the PHYpreamble of uplink data units. Thus, this allows omission of theHEW-SIGBs from UL OFDMA data units.

In some embodiments, the HEW-SIGBs are positioned after the HEW-LTFs814. In such embodiments, each HEW-SIGB 811 occupies an entire bandwidthof the corresponding OFDM data unit 802. In such embodiments,beamforming is applied to different spatial streams to shape, orbeamform, HEW-SIGBs 811 over the corresponding spatial streams toparticular client stations 25.

In some embodiments, further signal (SIG) fields are included in the PHYpreamble and positioned after the HEW-LTFs 730. In such embodiments,beamforming is applied to different spatial streams to shape, orbeamform, the further SIG fields over the corresponding spatial streamsto particular client stations 25.

In some embodiments and/or scenarios, the same color is assigned to allvirtual APs (corresponding to a single physical AP) to address problemswith different virtual APs having different colors discussed above. Forexample, in some embodiments, the physical AP (e.g., the host processor15) is configured to assign the same color to all of the correspondingvirtual APs. FIG. 9 is a message sequence diagram illustrating multipletransmissions among STA1, STA2, a first virtual AP (AP1) and a secondvirtual AP (AP2), according to an embodiment. In this embodiment, allvirtual APs associated with the same physical AP use the same BSS color.In an embodiment, AP1 and AP2 operate like the virtual APs 35-1 and 35-2of FIG. 1, and STA1 and STA2 are configured like the client devices 25.STA1 is associated with AP1, whose BSS color will be referred to asColor 1, and STA2 is associated with AP2, which has the same BSScolor—Color 1. At time t1, STA1 begins transmitting an HE PPDU 904 toAP1. At time t2, AP1 transmits a Block Acknowledgement (BA) 908 inresponse to the PPDU 904. At time t3, carries out a CCA procedure todetermine whether the channel is clear. In carrying out the CCAprocedure, STA2 detects PPDU 904, and measures the energy of PPDU 904 asbeing above the standard CCA threshold level (e.g., −82 dBm), but belowthe dynamic CCA level (e.g., −62 dBm). STA2 decodes the color field inthe PHY preamble of PPDU 904 and identifies the BSS color associatedwith PPDU 904 as Color 1. Because Color 1 is also the BSS colorassociated with AP2, STA2 uses the standard CCA level (e.g., −82 dBm).Because the measured energy of PPDU 904 is greater than the standard CCAlevel, STA2 concludes that the communication medium is busy andinitiates a back-off procedure, during which STA2 will not decrement abackoff counter of STA2. In an embodiment, STA2 also uses virtualcarrier sensing to decide whether the backoff counter of STA2 should bedecremented, e.g., when a network allocation vector (NAV) timer is notzero, STA2 is not permitted to decrement the backoff counter. Just afterthe end of BA 908, STA2 repeats the CCA procedure described above anddetermines that the communication medium is clear (e.g., overall energylevel is below −62 dBm and the 802.11-based energy level is below −82dBm). After the end of BA 908, the NAV timer of STA2 also becomes zeroand thus STA2 can resume decrementing the backoff counter. At time t4,based on the determination that the communication medium is clear andthat the backoff counter is zero, STA2 transmits an HE PPDU 912 to AP2.At time t5, AP2 transmits a BA 916 in response to the PPDU 912.

In embodiments in which each virtual AP corresponding to a singlephysical AP has a same color, OFDMA and/or MU-MIMO techniques may beutilized for simultaneous transmissions corresponding to differentvirtual APs. FIG. 10A is a diagram illustrating OFDMA transmissionsbetween three client devices, STA1, STA2, and STA3, and two virtual APs,AP1 and AP2, which are implemented by the same physical AP, according toan embodiment. In the scenario illustrated in FIG. 10A, the physical APsends DL traffic from virtual AP1 and virtual AP2 in a single DL OFDMAtransmission 930. In FIG. 10A, STA1 and STA3 are associated with AP1while STA2 is associated with AP2. The BSS color for AP1 is a valueColor 1 and the BSS color for AP2 is also the value Color 1. At time t1,the physical AP transmits an A-MPDU 934 (corresponding to virtual AP1and with the BSS color field set to Color 1) via DL OFDMA 930 to STA3via a 20 MHz channel of AP1, and an A-MPDU 938 (corresponding to virtualAP1 and with the BSS color field set to Color 1) to STA1 using a primary20 MHz channel (which is also the primary channel for AP2). The A-MPDU934 has a 20 MHz bandwidth, whereas the A-MPDU 938 has a 10 MHzbandwidth.

Also at time t1, AP2 transmits an A-MPDU 942 via the DL OFDMA data unit930 (with the BSS color bits set to Color 1) to STA2 using the primary20 MHz channel of AP2. At time t2, STA1, STA2, and STA3 transmit a blockacknowledgement (BA) 946 to virtual AP1 and virtual AP2.

FIG. 10B is a diagram showing a portion of the DL OFDMA transmission 930of FIG. 10A. In particular, FIG. 10B illustrates the portion of the DLOFDMA transmission 930 to STA1 and STA2. In particular, because virtualAP1 and virtual AP2 utilize the same color value (Color 1), a singleHE-SIGA 954 (which includes a BSS color field set to Color 1) can beutilized for the A-MPDU 938 from virtual AP1 to STA1 and the A-MPDU 942from virtual AP2 to STA2.

FIG. 11A is a diagram illustrating OFDMA transmissions between threeclient devices, STA1, STA2, and STA3, and two virtual APs, AP1 and AP2,which are implemented by the same physical AP, according to anembodiment. In the scenario illustrated in FIG. 11A, the AP associationsand BSS colors are the same as those described in conjunction with FIG.10A. At time t0, either AP1 or AP2 (or both) transmits SYNC frames 960to prompt UL OFDMA transmissions from STA1, STA2, and STA3 starting at atime t1. In response to the SYNC frames 960, at time t1, STA3 transmitsan A-MPDU 964 to AP1, STA2 transmits an A-MPDU 968 to AP2, and STA1transmits an A-MPDU 972 to AP1. A-MPDU 964, A-MPDU 968, and A-MPDU 972form an UL OFDMA data unit 976. At time t2, in response to the UL OFDMAdata unit 976, the physical AP transmits BAs 980 to STA1, STA2, andSTA3, e.g., AP1 transmits BAs to STA1 and STA3, while AP2 transmits a BAto STA2.

FIG. 11B is a set of diagrams illustrating the UL transmissions of STA1and STA2 of FIG. 11A, according to an embodiment. For example, thetransmission 968 is from STA2 to virtual AP2, whereas the transmission972 is from STA1 to virtual AP1. Transmission 968 includes an HE-SIGA990 with a BSS color field set to Color 1, and transmission 972 includesan HE-SIGA 992 with a BSS color field set to Color 1. Thus, HE-SIGA 990is the same as HE-SIGA 992, in some embodiments.

Transmission 968 also includes an A-MPDU 996 with data corresponding toAP2, and transmission 972 includes an A-MPDU 998 with data correspondingto AP1.

In some embodiments, a physical AP determines a plurality of respectivecolors of a plurality of respective BSSs corresponding to a plurality ofrespective virtual APs implemented by the AP device. For example, insome embodiments, the AP assigns respective colors to respective virtualAPs. Then, the physical AP device notifies client devices of therespective colors corresponding to the respective BSSs of the pluralityof virtual APs of the physical AP, according to some embodiments. Then,when a client device is performing a CCA procedure, the client devicecan determine whether a transmission associated with a different colorthan the BSS with which the client device is associated corresponds tothe same physical AP.

FIG. 12 is a message sequence diagram illustrating multipletransmissions among STA1, STA2, a first virtual AP (AP1) and a secondvirtual AP (AP2), according to an embodiment. In this embodiment, aphysical AP that operates multiple virtual APs assigns each virtual AP aBSS color and broadcasts a message 1002 that includes the BSS color ofeach of the virtual APs. In an embodiment, the colors of the two virtualAPs are different—AP1 having Color 1 and AP2 having Color 2, forexample. In an embodiment, AP1 and AP2 operate like the virtual APs 35-1and 35-2 of FIG. 1, and that STA1 and STA2 are configured like theclient devices 25. STA1 is associated with AP1 and STA2 is associatedwith AP2.

At time t0, either, or both of, AP1 and AP2 broadcasts a message 1002(e.g., a beacon or another suitable management frame) that lists the BSScolors of each of the virtual APs that are implemented by the physicalAP and corresponding BSSIDs, e.g. Color 1 and a BSSID1 of AP1, Color 2and a BSSID2 of AP2. In the example illustrated in FIG. 12, the list ofcolors and matched BSSIDs in the message includes Color 1 BSSID1 of AP1,as well as Color 2 BSSID2 of AP2. In an embodiment, a first entry in thelist indicates that AP1 has a BSS color of Color 1 and a second entry inthe list indicates that AP2 has a BSS color of Color 2. In anembodiment, the management frame also indicates a single color to beused in UL MU transmissions by stations, and a single color that will beused by AP1 and AP2 in DL MU transmissions. For example, in oneembodiment, STAs are configured to recognize that UL MU transmissionsshould utilize the color of the virtual AP that transmitted themanagement frame 1002 (e.g., the beacon), and that AP1 and AP2 will bothuse the color of the virtual AP that transmitted the management frame1002 in DL MU transmissions. In another embodiment, the STAs areconfigured to utilize a predetermined color value (e.g., a maximum colorvalue, a minimum color value, or some other suitable predetermined colorvalue) for UL MU transmissions; and the STAs are configured to recognizethat AP1 and AP2 will utilize the same predetermined color value (oranother suitable predetermined color value) for DL MU transmissions.

At time t1, STA1 begins transmitting an HE PPDU 1004 to AP1. At time t2,AP1 transmits a Block Acknowledgement (BA) 1008 in response to the PPDU1004. At time t1, STA2 detects the PPDU 1004, and measures the energy ofthe PPDU 1004 as being above the standard CCA threshold level (e.g., −82dBm), but below the dynamic CCA level (e.g., −62 dBm). STA2 decodes acolor field in a PHY preamble of the PPDU 1004 and identifies the BSScolor of the PPDU 1004 as being Color 1. STA2 then selects which CCAlevel to use—standard or dynamic—depending on the list of colorsprovided in the message 1002 at time t0. For example, if Color 1 wasincluded in the list of colors in message 1002, then STA2 knows thatPPDU 1004 corresponds to a BSS implemented by the same physical AP towhich STA2 is associated, and therefore uses the standard CCA level(e.g., −82 dBm). In the example illustrated in FIG. 12, at t1, themeasured energy of the PPDU 1004 is greater than the standard CCA level.STA2 therefore concludes that the medium is busy. STA2 also sets NAVtimer of STA2 per a Duration field in a frame in the detected PPDU 1004if the energy of the PPDU 1004 is higher than the CCA level. At t3,STA2, which has frame for transmission, initiates a back-off procedureand sets a backoff counter. Just after the end of BA 1008, STA2 repeatsthe CCA procedure described above and determines that the medium isclear (e.g., overall energy level is below −62 dBm and the 802.11-basedenergy level is below −82 dBm). Therefore, STA2 begins decrementing thebackoff counter. At time t4, based on a determination that the backoffcounter is zero, STA2 transmits an HE PPDU 1012 to AP2. At time t5, AP2transmits a BA 1016 in response to the PPDU 1020.

With the help of management frame that notifies the color used in UL MUtransmission and DL MU transmission, A-MPDUs from/to multiple virtualAPs with different BSS colors can be transmitted in one MU transmission.FIG. 13A is a diagram illustrating OFDMA transmissions between threeclient devices, STA1, STA2, and STA3, and two virtual APs, AP1 withColor 1 and AP2 with Color 2, which are implemented by the same physicalAP, according to an embodiment. In the scenario illustrated in FIG. 13A,Color 1 and Color 2 are different. At time t0, AP1 or AP2 (or both)broadcasts (e.g., in a beacon 1050 or another suitable management frame)a color value that is to be used for MU transmission, e.g., Color 1. Attime t1, either AP1 or AP2 (or both) transmits SYNC frames 1060 toprompt UL OFDMA transmissions from STA1, STA2, and STA3 starting at atime t2. In response to the SYNC frames 1060, at time t2, STA3 transmitsan A-MPDU 1064 to AP1 and Color 1 is included in a color field of PHYSIG of the PPDU that carry A-MPDU 1064, STA2 transmits an A-MPDU 1068 toAP2 and Color 1 is included in a color field in PHY SIG of the PPDU thatcarry A-MPDU 1068, and STA1 transmits an A-MPDU 1072 to AP1 and Color 1is included in a color field of PHY SIG of the PPDU that carry A-MPDU1072. A-MPDU 1064, A-MPDU 1068, and A-MPDU 1072 form an UL OFDMA dataunit 1076. So the HE SIGs transmitted by STA1, STA2 and STA3 are same,in an embodiment. At time t3, in response to the UL OFDMA data unit1076, the physical AP transmits BAs 1080 to STA1, STA2, and STA3 andColor 1 is included in a color field of PHY SIG of the PPDU that carriesBAs 1080, e.g., AP1 transmits BAs to STA1 and STA3, while AP2 transmitsa BA to STA2. So the HE SIGs transmitted by AP1 and AP2 in connectionwith the BAs 1080 are the same, in an embodiment.

FIG. 13B is a set of diagrams illustrating the UL transmissions of STA1and STA2 of FIG. 13A, according to an embodiment. For example, thetransmission 1068 is from STA2 to virtual AP2, whereas the transmission1072 is from STA1 to virtual AP1. Transmission 1068 includes an HE-SIGA1090 with a BSS color field set to Color 1, and transmission 1072includes an HE-SIGA 1092 with a BSS color field set to Color 1. Thus,HE-SIGA 1090 is the same as HE-SIGA 1092, in some embodiments.

Transmission 1068 also includes an A-MPDU 1096 with data correspondingto AP2, and transmission 1072 includes an A-MPDU 1098 with datacorresponding to AP1.

FIG. 14 is a flow diagram of an example method 1300 for informing clientdevices of a physical AP of BSS identifiers (e.g., colors) of virtualAPs implemented by the physical AP, according to an embodiment. In someembodiments, the method 1300 is implemented by the AP 14 (FIG. 1). Forexample, in some embodiments, the network interface device 16 isconfigured to implement the method 1300. As another example, in someembodiments, the host 15 is configured to implement at least a portionof the method 1300. As another example, in some embodiments, the host 15and the network interface device 16 are configured to implement themethod 1300. In other embodiments, another suitable communication deviceis configured to implement the method 1300.

At block 1304, a plurality of respective identifiers (e.g., colors) of aplurality of respective BSSs corresponding to a plurality of respectivevirtual APs implemented by a physical AP device are determined.

At block 1308, the plurality of respective identifiers (e.g., colors)determined at block 1304 are communicated to client devices of thephysical AP so that client devices of the plurality of virtual APs aremade aware of all of the identifiers of the plurality of respectiveBSSs. In some embodiments, block 1308 also includes indicating to STAs asingle color value that is to be used by STAs for MU UL transmissions.In some embodiments, block 1308 also includes indicating to STAs asingle color value that will be used by virtual APs for MU DLtransmissions. In some embodiments, the single color value that is to beused by STAs for MU UL transmissions is the same as the single colorvalue that will be used by virtual APs for MU DL transmissions. In someembodiments, block 1308 comprises communicating the BSS identifiers ofall of the BSSs in a single message. For example, in an embodiment, alist of the BSS identifiers of all of the BSSs (and correspondingBSSIDs) is included in a single physical layer data unit that isbroadcast by the physical AP to the client devices of the physical AP.In some embodiments, the single message (e.g., the single PPDU) alsoindicates the single color value that is to be used by STAs for MU ULtransmissions and/or indicates the single color value that virtual APswill use for MU DL transmissions. In some embodiments, the single colorvalue that is to be used by STAs for MU UL transmissions is the same asthe single color value that will be used by virtual APs for MU DLtransmissions. In some embodiments, the list of the BSS identifiers ofall of the BSSs (and optionally one or more of i) the correspondingBSSIDs, ii) the indication of the single color value that is to be usedby STAs for MU UL transmissions, and/or iii) the single color value thatwill be used by virtual APs for MU DL transmissions) is included in abeacon frame or another suitable management frame. In some embodiments,respective portions of the list of the BSS identifiers of all of theBSSs (and optionally one or more of i) the corresponding BSSIDs, ii) theindication of the single color value that is to be used by STAs for MUUL transmissions, and/or iii) the single color value that will be usedby virtual APs for MU DL transmissions) are included in respectivedifferent physical layer data units transmitted by the physical AP atdifferent times.

In some embodiments, the method 1300 further includes assigning theplurality of respective identifiers (e.g., colors) to the plurality ofrespective BSSs corresponding to the plurality of respective virtualAPs. In some embodiments, the method 1300 further includes assigning aplurality of respective BSSIDs to the plurality of virtual APs. In someembodiments, the method 1300 further includes setting up the pluralityof virtual APs at the physical AP.

According to an embodiment, each virtual AP collocated in the samephysical AP uses identical values in a first set of bits (e.g., one ofthe most significant bits or the least significant bits) of a BSS colorvalue, whereas each virtual AP collocated in the same physical AP usesdifferent values in a second set of bits (e.g., the other of the mostsignificant bits or the least significant bits) of the BSS color value.For instance, in an illustrative embodiment, a BSS color field comprisestwo parts: m least significant bits (also referred to as a “virtual APID part”), which are used to identify virtual APs, and n-m mostsignificant bits (also referred to as the “segment ID part”), which areused to identify a common physical AP for the virtual APs. Each virtualAP, in this embodiment, has identical values for the segment ID part,but a unique (at least for that physical AP) value for the virtual IDpart.

FIG. 15 is a message sequence diagram illustrating multipletransmissions among STA1, STA2, a first virtual AP (AP1) and a secondvirtual AP (AP2), according to an embodiment. At time t1, STA1 beginstransmitting an HE PPDU 1304 to AP1. At time t2, AP1 transmits a BlockAcknowledgement (BA) 1308 in response to the PPDU 1304. A color field ina PHY preamble of the PPDU 1304 is set to a value Color 1. In anembodiment, a first set of bits of the value Color 1 corresponds to asegment ID set to a value x, and a second set of bits of the value Color1 corresponds to a virtual ID set to a value y.

At time t1, STA2 detects the PPDU 1304, and measures the energy of thePPDU 1304 as being above the standard CCA threshold level (e.g., −82dBm), but below the dynamic CCA level (e.g., −62 dBm). STA2 decodes thesegment ID part of the color field of the PHY preamble of the PPDU 1304and determines that the segment ID is the same as a segment ID of acolor of a BSS to which STA2 is associated (e.g., Color 2, where a firstset of bits of the value Color 2 corresponds to a segment ID set to thevalue x, and a second set of bits of the value Color 2 corresponds to avirtual ID set to a value z). STA2 therefore uses the standard CCAlevel. Because the measured energy of the PPDU 1304 is greater than thestandard CCA level, STA2 concludes that the channel is busy and sets aNAV timer per duration field(s) in the detected MPDUs carried in PPDU1304. At time t4, a back-off counter of STA2 becomes zero. So at timet5, STA2 transmits an HE PPDU 1312 to AP2. At time t6, AP2 transmits aBA 1316 in response to the PPDU 1312.

FIG. 16 is a flow diagram of an example method 1500 for performing a CCAprocedure, according to an embodiment. In some embodiments, the method1500 is implemented by the client device 25-1 (FIG. 1) and/or the AP 14.For example, in some embodiments, the network interface device 16 isconfigured to implement the method 1500. As another example, in someembodiments, the host 15 and the network interface device 16 areconfigured to implement the method 1500. For example, in someembodiments, the network interface device 27 is configured to implementthe method 1500. As another example, in some embodiments, the host 26and the network interface device 27 are configured to implement themethod 1500. In other embodiments, another suitable communication deviceis configured to implement the method 1500.

At block 1504, a signal is received. At block 1508, it is determinedwhether the signal is a signal that conforms to a particular one or morecommunication protocols recognized by the client device 25-1. Forexample, in an embodiment, it is determined whether the signal conformsto a WiFi communication protocol. As another example, in an embodiment,it is determined whether the signal conforms to a communication protocoldefined by the IEEE 802.11 Standard. In other embodiments, it isdetermined whether the signal conforms to another suitable communicationprotocol. Block 1508 comprises analyzing the signal to determine whetherthe signal includes a PHY preamble that conforms to a particularcommunication protocol, or to one of several particular communicationprotocols, in various embodiments.

If it is determined at block 1508 that the signal is not a signal thatconforms to the particular communication protocol (or one of severalcommunication protocols, in some embodiments) recognized by the clientdevice 25-1, the flow proceeds to block 1512. At block 1512, an energylevel of the signal is compared a first threshold as part of the CCAprocedure. The first threshold is lower than a second threshold alsoused as part of the CCA procedure, as will be described below.

On the other hand, if it is determined at block 1508 that the signal isa signal that conforms to the particular communication protocol (or oneof several communication protocols, in some embodiments) recognized bythe client device 25-1, the flow proceeds to block 1516. At block 1516,a color field in a PHY preamble of the signal is decoded to determine acolor value corresponding to the signal received at block 1504.

At block 1520, it is determined whether the color value determined atblock 1516 corresponds to a color value corresponding to a physical APwith which the client 25-1 is associated. For example, in one scenario,the client 25-1 is associated with a first BSS managed by a firstvirtual AP1 implemented by the physical AP, where the first BSS has acolor value Color 1. In embodiments in which all BSSs managed by virtualAPs implemented by the physical AP have the same color, the client 25-1compares the color value determined at block 1516 with the value Color 1and if the color value determined at block 1516 is not Color 1, theclient 25-1 determines that the signal received at block 1516 does notcorrespond to the same physical AP. On the other hand, in suchembodiments, if the color value determined at block 1516 is Color 1, theclient 25-1 determines that the signal received at block 1516corresponds to the same physical AP.

In embodiments in which BSSs managed by virtual APs implemented by thephysical AP have different colors, and the physical AP previouslyprovided the client 25-1 with the color values of the BSSs of thevirtual APs implemented by the physical AP, the client 25-1 compares thecolor value determined at block 1516 with the color values provided bythe physical AP. For example, after receiving the color values of theBSSs of the virtual APs implemented by the physical AP, the clientdevice 25-1 stores the color values in a memory of or associated withthe network interface device 27. Then, the client device 25-1 accessesthe color values in the memory as part of implementing block 1520. Ifthe color value determined at block 1516 does not match any of the colorvalues provided by the physical AP, the client 25-1 determines that thesignal received at block 1504 does not correspond to the same physicalAP. On the other hand, in such embodiments, if the color valuedetermined at block 1516 matches one of the color values provided by thephysical AP, the client 25-1 determines that the signal received atblock 1504 corresponds to the same physical AP.

In embodiments in which BSSs managed by virtual APs implemented by thephysical AP have colors values in which a respective first part of theeach color value has a same value (e.g., a segment ID part) and arespective second part of each color value has a different value (e.g.,a virtual ID part), the client 25-1 compares a first part of the colorvalue determined at block 1516 with a first part of Color 1. If thefirst part of the color value determined at block 1516 is different thanthe first part of Color 1, the client 25-1 determines that the signalreceived at block 1504 does not correspond to the same physical AP. Onthe other hand, in such embodiments, if the first part of the colorvalue determined at block 1516 is the same as the first part of Color 1,the client 25-1 determines that the signal received at block 1504corresponds to the same physical AP.

If it is determined at block 1520 that signal received at block 1504does not correspond to the same physical AP, the flow proceeds to block1512. On the other hand, if it is determined at block 1520 that signalreceived at block 1504 does correspond to the same physical AP, the flowproceeds to block 1524. At block 1524, the energy level of the signal iscompared the second threshold as part of the CCA procedure, where thesecond threshold is higher than the first threshold.

In some embodiments, OFDMA transmissions with multiple BSS colors arenot permitted. Thus, in some embodiments, a physical AP is not permittedto transmit data corresponding to different BSSs with different colorsin a single DL OFDMA PHY data unit. Similarly, in some embodiments,client devices corresponding to different BSSs with different colors arenot permitted to transmit as part of a single UL OFDMA transmission.

In some embodiments, to avoid the limitation discussed above withrespect to OFDMA transmissions and different BSS colors, a physical APmay select a single color value for UL/DL MU transmissions and notifiesthe STAs of the selected color value. The physical AP sets color fieldsin PHY preamble of a DL OFDMA data unit to the single value even thoughthe DL OFDMA data unit includes transmissions corresponding to multipleBSSs with different color values. The STAs associated with differentvirtual APs set color fields in PHY preamble of a UL OFDMA data unit tothe selected single value even though the UL OFDMA data unit includestransmissions corresponding to multiple BSSs with different colorvalues.

FIG. 17 is a flow diagram of an example method 1600 for performing anOFDMA transmission, according to an embodiment. In some embodiments, themethod 1600 is implemented by the AP 14 (FIG. 1). For example, in someembodiments, the network interface device 16 is configured to implementthe method 1600. As another example, in some embodiments, the host 15 isconfigured to implement at least a portion of the method 1600. Asanother example, in some embodiments, the host 15 and the networkinterface device 16 are configured to implement the method 1600. Inother embodiments, another suitable communication device is configuredto implement the method 1600.

At block 1604, a plurality of identifiers (e.g., color values) of aplurality of respective BSSs are determined, the respective BSSscorresponding to a plurality of respective virtual APs implemented by aphysical AP device. In an embodiment, one of the plurality ofidentifiers is selected for MU transmissions and the AP device notifiesSTAs of the selected identifier.

At block 1608, an OFDMA PHY data unit is generated, wherein the OFDMAPHY data unit is generated to include data from multiple virtual APsamong the plurality of virtual APs. Block 1608 includes generating a PHYpreamble that includes one or more fields for specifying an identifierof a BSS, wherein the one or more fields are set to a same value (e.g.,the selected identifier).

For example, in an embodiment, one identifier from the plurality ofrespective identifiers of the plurality of respective BSSs is selected,and the one or more fields in the PHY preamble are set to the selectedone identifier.

As another example, in some embodiments, each identifier includes arespective first set of bits and a respective second set of bits, andblock 1604 includes determining the respective first sets of bits to bea same first value and determining the respective second sets of bits tobe respective second values. In some embodiments, block 1608, each ofthe one or more fields in the PHY preamble has a first set of bits setto the same first value and a second set of bits set to a third valuedifferent than all of the respective second values. As an illustrativeexample, the third value is zero, whereas all of the respective secondvalues are non-zero values, according to an embodiment. In otherembodiments, however, the third value is a suitable non-zero value(e.g., all ones).

At block 1612, the OFDMA PHY data unit is transmitted to a group ofclient devices among the plurality of client devices.

To respond to the OFDMA PHY data unit transmitted at block 1612, in anembodiment, the respective client devices transmit an acknowledgment tothe physical AP using the same BSS identifier as the BSS identifier usedin the OFDMA PHY data unit transmitted at block 1612. For example,referring to FIG. 10A, at time t2, all of the stations respond to the DLOFDMA transmission 930 in the single UL OFDMA transmission 946 using theBSS color in the PHY preamble of the DL OFDMA 930.

Referring again to FIG. 17, in some embodiments, the method 1600includes other acts such as one or more of: setting up the plurality ofvirtual APs, assigning the plurality of identifiers to the BSSs, withthe plurality of client devices, etc., according to various embodiments.

As another example, in an embodiment, the method 1600 further includesgenerating a single user PHY data unit corresponding to only one virtualAP, wherein generating the single user PHY data unit comprisesgenerating a PHY preamble of the single user PHY data unit that includesone or more fields for specifying an identifier of a BSS, wherein theone or more fields are set to the identifier corresponding to the onevirtual AP, and wherein the identifier corresponding to the one virtualAP is different than the same value in the PHY preamble of the OFDMA PHYdata unit; and transmitting the single user PHY data unit to one of theclient devices among the plurality of client devices.

FIG. 18 is a flow diagram of an example method 1700 for performing anOFDMA transmission, according to an embodiment. In some embodiments, themethod 1700 is implemented by the client device 25-1 (FIG. 1). Forexample, in some embodiments, the network interface device 27 isconfigured to implement the method 1700. As another example, in someembodiments, the host 26 and the network interface device 16 areconfigured to implement the method 1700. In other embodiments, anothersuitable communication device is configured to implement the method1700.

At block 1704, the communication device 25-1 associates with a virtualAP implemented by a physical AP, the virtual AP corresponding to a firstBSS, wherein the first BSS corresponds to a first BSS identifier (e.g.,a first color value (Color 1)).

At block 1708, as part of an OFDMA transmission (e.g., an UL OFDMAtransmission to the physical AP), a signal is generated, the signalhaving i) a PHY preamble with a field including a second BSS identifier(e.g., a second color value (Color 2), and ii) a PHY payloadcorresponding to the first BSS.

For example, in an embodiment, the second BSS identifier corresponds toa second BSS of another virtual AP implemented by the physical AP. Forinstance, in an embodiment, a set of BSS identifiers is previouslyreceived from the physical AP, wherein the set of BSS identifiersinclude identifiers of BSSs corresponding to BSSs of a set of virtualAPs implemented by the physical AP, the second BSS identifier isselected from the set of identifiers received from the physical AP. Asan illustrative embodiment, the physical AP indicates that the secondBSS identifier, from among the list of BSS identifiers, should be usedfor UL OFDMA transmissions. For instance, in an embodiment, the secondBSS identifier is at a position in (e.g., a top of) the list of BSSidentifiers, where the position in the list indicates that the secondBSS identifier should be used for UL OFDMA transmissions. In anotherembodiment, the second BSS identifier is flagged in the list of BSSidentifiers, where the flagging of the second BSS identifier indicatesthat the second BSS identifier should be used for UL OFDMAtransmissions.

In some embodiments, the physical AP previously informs the clientdevice 25-1 to use the second BSS identifier (in PHY preambles) whenparticipating in UL OFDMA transmissions via one or more of a broadcastframe, a management frame, a control frame, a beacon frame, etc. In anembodiment, the physical AP informs the client device 25-1 to use thesecond BSS identifier (in PHY preambles) when participating in the ULOFDMA transmission via a SYNC frame that also prompts the client device25-1 to transmit the signal at block 1708 as part of the UL OFDMAtransmission.

As another example, in some embodiments, a first set of bits of thesecond BSS identifier is equal to a corresponding first set of bits ofthe first BSS identifier; and a second set of bits of the second BSSidentifier is different than a corresponding second set of bits of thefirst BSS identifier. For instance, in an embodiment, the client device25-1 sets the first set of bits of the second BSS identifier equal tothe corresponding first set of bits of the first BSS identifier, andsets the second set of bits of the second BSS identifier to apredetermined value that is different than the corresponding second setof bits of the first BSS identifier. In an embodiment, the predeterminedvalue is zero. In other embodiments, the predetermined value is anothersuitable value other than zero (e.g., all ones).

At block 1712, the signal is transmitted to the physical AP as part ofthe UL OFDMA transmission. For example, in an embodiment, the signal istransmitted simultaneously with other transmissions from other clientdevices, the other transmissions also being part of the UL OFDMAtransmission.

To respond to the OFDMA PHY data unit transmitted at block 1712, in anembodiment, the physical AP transmits an OFDMA acknowledgment to theclient devices using the same BSS identifier as the BSS identifier usedin the OFDMA PHY data unit transmitted at block 1712. For example,referring to FIG. 11A, at time t2, the physical AP responds to the ULOFDMA transmission 976 in the single DL OFDMA transmission 980 using theBSS color that was included in the PHY preamble of the UL OFDMA 976.

Referring again to FIG. 18, in some embodiments, the method 1700 alsoincludes one or more other acts, such as receiving a SYNC frame thatprompts the transmission at block 1712 as part of the UL OFDMAtransmission, exchanging single user PHY data units with the physicalAP, wherein the single user PHY data units include PHY preambles, eachPHY preamble having a field including the first BSS identifier, etc. Insome embodiments in which the method 1700 includes receiving a SYNCframe that prompts the transmission at block 1712, the SYNC frameindicates that the client device is to use the second BSS identifier inthe PHY preamble of the signal generated at block 1708.

In an embodiment, when the BSS colors of all of the virtual APs of agiven physical AP are advertised by the physical AP and a selected colorto be used for MU transmissions through the use of a Multiple BSS Colorelement (e.g., a set of BSS color bits for each separate virtual APtransmitted via a beacon, or a set of BSS colors and correspondingBSSIDs for each separate virtual AP transmitted via beacon, and anindication of a selected color for MU transmissions), the client devicessend the UL traffic to the virtual APs on a single OFDMA UL transmissionusing the following rules: (1) The physical AP transmits a managementframe that indicates a color for UL OFDMA (e.g. in a Multiple BSS Colorelement) or a SYNC frame that indicates a BSS color for UL OFDMA. (2)All STAs that associate with a virtual BSS need to receive the SYNC,which may originate from any of the virtual APs on that physical AP(i.e., any virtual AP defined in the Multiple BSSID elementtransmission—e.g., the beacon). In another embodiment, the STAs do notrespond in a single UL OFDMA transmission, but rather in separate singleuser transmissions.

According to an embodiment, each virtual AP collocated in the samephysical AP use identical values in a sub-portion (e.g., the mostsignificant bits or the least significant bits) of a BSS color field. Inan embodiment, the BSS color field is separated to two parts: m leastsignificant bits (also referred to as a “virtual AP ID part”), which areused to identify virtual APs, and n-m most significant bits (alsoreferred to as the “segment ID part”), which are used to identify acommon physical AP for the virtual APs. Each virtual AP in thisembodiment has identical values for the segment ID part, but a unique(at least for that physical AP) value for the virtual ID part. In anembodiment, the virtual AP ID part is the same for all virtual APs of asingle physical AP. In another embodiment, the virtual AP ID part isdifferent for each virtual AP on the single physical AP.

In some embodiments, the physical AP uses one value of the virtual AP IDpart for the color value included in a PHY preamble of a DL OFDMAcommunication, e.g., all zeros in virtual AP ID part, all ones in thevirtual AP ID part, etc.

In one embodiment, a method for communicating on a wireless networkincludes, on a physical access AP: setting up a plurality of virtualAPs; assigning a basic service set (BSS) color to each of the pluralityof virtual APs; and broadcasting a message that identifies each of theplurality of APs and the BSS color assigned to each of the plurality ofAPs.

In other embodiments, the method includes one of, or any suitablecombination of two or more of, the following features.

The method also includes transmitting, to a first client device onbehalf of a first virtual AP of the plurality of virtual APs, a firstpacket data unit comprising a header, wherein the header comprises datarepresenting the color of the first virtual AP; and transmitting, to asecond client device on behalf of a second virtual AP of the pluralityof virtual APs, a second packet data unit comprising a header, whereinthe header comprises data representing the BSS color of the secondvirtual AP.

The physical AP transmits the first and second packet data units in asingle downlink orthogonal frequency division multiple access (OFDMA)transmission.

The BSS color assigned to the first virtual AP is identical to the BSScolor assigned to the second virtual AP; and the method furtherincludes: transmitting, to a first client device on behalf of a firstvirtual AP of the plurality of virtual APs, a first packet data unitcomprising a header, wherein the header comprises data representing theBSS color; and transmitting, to a second client device on behalf of asecond virtual AP of the plurality of virtual APs, a second packet dataunit comprising a header, wherein the header comprises data representingthe BSS color.

The method further includes receiving, in response to the first andsecond packet data units, a single uplink OFDMA transmission from thefirst and second client devices, wherein the uplink OFDMA transmissioncomprises packet data unit from the first client device and a packetdata unit from the second client device, and wherein the packet dataunit from the first client device includes a header comprising the BSScolor and the packet data unit from the second client device includes aheader comprising the BSS color.

The method further includes selecting a BSS color of the first virtualAP or the BSS color of the second virtual AP; transmitting, on behalf ofat least one of the plurality of virtual APs, a SYNC message, whereinthe SYNC message identifies the selected BSS color to be the BSS colorof the SYNC message; and receiving, in response to the SYNC message, anuplink OFDMA transmission from a plurality of client devices, whereinthe uplink OFDMA transmission comprises a header including the selectedBSS color.

The method further includes transmitting, in response to the uplinkOFDMA transmission, an ACK comprising data representing the BSS color.

The BSS color assigned to the first virtual AP is identical to the BSScolor assigned to the second virtual AP.

In another embodiment, a method for communicating on a wireless network,the method includes, on a physical AP: setting up a plurality of virtualAPs; assigning a BSS color to each of the plurality of virtual APs, suchthat: the BSS color of each virtual AP is divided into at least avirtual AP identifier part and a segment identifier part, and thevirtual AP identifier is the same for each virtual AP; transmitting, onbehalf of the first virtual AP, a first packet data unit to a firstclient device, wherein a header of the first packet data unit includesthe BSS color assigned to the first virtual AP; and transmitting, onbehalf of the second virtual AP, a second packet data unit to a secondclient device, wherein a header of the second packet data unit includesthe BSS color assigned to the second virtual AP.

In other embodiments, the method includes one of, or any suitablecombination of two or more of, the following features.

The method further comprises transmitting, on behalf of a first virtualAP of the plurality of virtual APs, a first packet data unit comprisinga PHY header, wherein the PHY header comprises data representing thecolor of the first virtual AP; and transmitting, on behalf of a secondvirtual AP of the plurality of virtual APs, a second packet data unitcomprising a header, wherein the header comprises data representing theBSS color of the second virtual AP.

The physical AP transmits the first and second packet data units in asingle DL OFDMA transmission.

The method further comprises: selecting a BSS color of the first virtualAP or the BSS color of the second virtual AP; transmitting, on behalf ofat least one of the plurality of virtual APs, a SYNC message, whereinthe SYNC message identifies the selected BSS color to be the BSS colorof the SYNC message; and receiving, in response to the SYNC message, anuplink OFDMA transmission from a plurality of client devices, whereinthe uplink OFDMA transmission comprises a header including the selectedBSS color.

The method further comprises transmitting, in response to the uplinkOFDMA transmission, an ACK comprising data representing the BSS color.

In another embodiment, a method of determining whether a wirelesscommunication medium is clear includes, on client device: associatingwith a first virtual access point (AP) of a plurality of virtual APsimplemented by a physical AP; receiving, from a physical AP, a messageidentifying the basic service set (BSS) color of each of the pluralityof virtual APs implemented by the physical AP; detecting a packet dataunit; measuring the energy of the packet data unit; decoding a BSS colorfrom the packet data unit; if the decoded BSS color is the same as a BSScolor in the message from the physical AP, then setting an energythreshold to a first level; if the decoded BSS color is not the same asany BSS color in the message from the physical AP, then setting anenergy threshold to a second level, wherein the second level is higherthan the first level; and transmitting or refraining from transmitting apacket data unit based on a comparison of the measured energy and theenergy threshold.

In other embodiments, the method includes one of, or any suitablecombination of two or more of, the following features.

The received message is a beacon; and the method further includes:detecting the packet data unit comprises detecting a packet data unittransmitted from a second virtual AP of the plurality of APs; decodingthe BSS color comprises decoding a header of the detected packet dataunit; identifying the BSS color as being one of the BSS colors containedin the beacon; and in response to identifying the BSS color as being oneof the BSS colors contained in the beacon, setting the energy thresholdto first level.

The first threshold level is a static clear channel assessment level.

The second threshold level is a dynamic clear channel assessment level.

In another embodiment, a method of determining whether a wirelesscommunication medium is clear includes, on a client device: associatingwith a first virtual access point (AP) of a plurality of virtual APsimplemented by a physical AP, wherein the first virtual AP has a virtualAP identifier; detecting a packet data unit that includes a headercomprising a basic service set (BSS) color field, wherein the BSS colorfield comprises a virtual AP identifier part and a segment identifierpart; measuring the energy of the packet data unit; decoding the virtualAP part; if the decoded virtual AP part is the same as the virtual APidentifier of the first virtual AP, then setting an energy threshold toa first level; if the decoded virtual AP part is not the same as thevirtual AP identifier of the first virtual AP, then setting an energythreshold to a second level, wherein the second level is higher than thefirst level; and transmitting or refraining from transmitting a packetdata unit based on a comparison of the measured energy and the energythreshold.

In other embodiments, the method includes one of, or any suitablecombination of two or more of, the following features.

Each of the plurality of virtual APs is assigned the same virtual APidentifier and the same segment identifier.

Each of the plurality of virtual APs is assigned a different virtual APidentifier and the same segment identifier.

At least some of the various blocks, operations, and techniquesdescribed above may be implemented utilizing hardware, a processorexecuting firmware instructions, a processor executing softwareinstructions, or any combination thereof. Examples of suitable hardwareinclude a microprocessor, microcontroller, application specificintegrated circuit (ASIC), field programmable gate array, programmablelogic device, etc. When implemented utilizing a processor executingsoftware or firmware instructions, the software or firmware instructionsmay be stored on a computer readable medium, or media, such as amagnetic disk, an optical disk, a random access memory (RAM), a readonly memory (ROM), a flash memory, a magnetic tape, etc. The software orfirmware instructions may include machine readable instructions that,when executed by one or more processors, cause the one or moreprocessors to perform various acts.

When implemented in hardware, the hardware may comprise one or more ofi) discrete components, ii) one or more integrated circuits, iii) one ormore application-specific integrated circuits (ASICs), iv) one or moreprogrammable logic devices, etc.

While the present disclosure has been described with reference tospecific examples, which are intended to be illustrative only and not tobe limiting of the invention, changes, additions and/or deletions may bemade to the disclosed embodiments without departing from the scope ofthe claims.

What is claimed is:
 1. A method, comprising: associating, at acommunication device, with a virtual access point (AP) implemented by aphysical AP, the virtual AP corresponding to a first basic service set(BSS), wherein the first BSS corresponds to a first BSS identifier; inconnection with an uplink (UL) orthogonal frequency division multipleaccess (OFDMA) transmission to the physical AP, generating, at thecommunication device, a signal having i) a physical layer (PHY) preamblewith a field set to a value of a second BSS identifier, and ii) a PHYpayload corresponding to the first BSS, wherein i) the value of thesecond BSS identifier is a BSS color value and ii) the second BSSidentifier corresponds to all virtual APs implemented by the physicalAP; and transmitting, with the communication device, the signal as partof the UL OFDMA transmission to the physical AP, wherein the signal istransmitted simultaneously with another signal, transmitted by anothercommunication device, that is part of the UL OFDMA transmission to thephysical AP and that includes a corresponding field of another PHYpreamble, wherein i) the corresponding field of the other PHY preambleis set to the value of the second BSS identifier and ii) the othersignal corresponds to another virtual AP implemented by the physical AP.2. The method of claim 1, further comprising: receiving, at thecommunication device, a set of identifiers from the physical AP, whereinthe set of identifiers include identifiers of BSSs corresponding to BSSsof a set of virtual APs implemented by the physical AP; and selectingthe second BSS identifier from the set of identifiers received from thephysical AP.
 3. The method of claim 1, wherein: a first set of bits ofthe second BSS identifier is equal to a corresponding first set of bitsof the first BSS identifier; and a second set of bits of the second BSSidentifier is different than a corresponding second set of bits of thefirst BSS identifier.
 4. The method of claim 3, further comprisinggenerating the second BSS identifier, including: setting the first setof bits of the second BSS identifier equal to the corresponding firstset of bits of the first BSS identifier; and setting the second set ofbits of the second BSS identifier to a predetermined value that isdifferent than the corresponding second set of bits of the first BSSidentifier.
 5. The method of claim 1, further comprising: exchanging,with the communication device, single user PHY data units with thephysical AP, wherein the single user PHY data units include PHYpreambles, each PHY preamble having a field including the first BSSidentifier.
 6. The method of claim 1, wherein the first BSS identifieris the BSS color value.
 7. An apparatus, comprising: a network interfacedevice associated with a communication device, having one or moreintegrated circuit devices configured to associate with a virtual accesspoint (AP) implemented by a physical AP, the virtual AP corresponding toa first basic service set (BSS), wherein the first BSS corresponds to afirst BSS identifier, in connection with an uplink (UL) orthogonalfrequency division multiple access (OFDMA) transmission to the physicalAP, generate a signal having i) a physical layer (PHY) preamble with afield set to a value of a second BSS identifier, and ii) a PHY payloadcorresponding to the first BSS, wherein i) the value of the second BSSidentifier is a BSS color value and ii) the second BSS identifiercorresponds to all virtual APs implemented by the physical AP, andtransmit the signal as part of the UL OFDMA transmission to the physicalAP, wherein the signal is transmitted simultaneously with anothersignal, transmitted by another communication device, that is part of theUL OFDMA transmission to the physical AP and that includes acorresponding field of another PHY preamble, wherein i) thecorresponding field of the other PHY preamble is set to the value of thesecond BSS identifier and ii) the other signal corresponds to anothervirtual AP implemented by the physical AP.
 8. The apparatus of claim 7,wherein the one or more integrated circuit devices are configured to:receive a set of identifiers from the physical AP, wherein the set ofidentifiers include identifiers of BSSs corresponding to BSSs of a setof virtual APs implemented by the physical AP; and select the second BSSidentifier from the set of identifiers received from the physical AP. 9.The apparatus of claim 7, wherein: a first set of bits of the second BSSidentifier is equal to a corresponding first set of bits of the firstBSS identifier; and a second set of bits of the second BSS identifier isdifferent than a corresponding second set of bits of the first BSSidentifier.
 10. The apparatus of claim 9, wherein the one or moreintegrated circuit devices are configured to: set the first set of bitsof the second BSS identifier equal to the corresponding first set ofbits of the first BSS identifier; and set the second set of bits of thesecond BSS identifier to a predetermined value that is different thanthe corresponding second set of bits of the first BSS identifier. 11.The apparatus of claim 7, wherein the one or more integrated circuitdevices are configured to: exchange single user PHY data units with thephysical AP, wherein the single user PHY data units include PHYpreambles, each PHY preamble having a field including the first BSSidentifier.
 12. The apparatus of claim 7, wherein the network interfacedevice comprises one or more transceivers.
 13. The apparatus of claim12, further comprising: one or more antennas coupled to the one or moretransceivers.
 14. The apparatus of claim 7, wherein the first BSSidentifier is the BSS color value.